You need Nascar Featherlite Trailer mod for use these skins.

https://atsmod.net/american-truck-simulator-mods/ats-trailers/nascar-haulers-2011-featherlite-trailer-v1-8-1-42/ 

I just ordered skin and paid.
Where Can I get my skin?

Once you've completed your order,  you could download your skin in your profile page right away.
https://x-skin.net/member/?mode=paypal 

How to apply downloaded skin

https://x-skin.net/community/info.html?query=view&uid=1261